Korea-US NanoForum 2010 ECC, Ewha Univ., Korea 2010. 4. 5-6 Q Quantum Dot-Conducting Polymer t D t C d ti P l Hybrids for Optoelectronic Devices H b id f O t l t i D i 2010. 4. 5. Changhee Lee School of Electrical Engineering and Computer Science Seoul National Univ. chlee7@snu.ac.kr eoul National University 1/23 CHANGHEE LEE | Organic S CHANGHEE LEE | Organic S emiconductor Lab. | S emiconductor Lab. | S eoul National University
Korea-US NanoForum 2010 Contents ECC, Ewha Univ., Korea 2010. 4. 5-6 • Introduction of semiconductor Quantum dots • Quantum Dot / Conducting Polymer Hybrid Material • Light-Emitting Diodes Based on QD-Polymer Hybrid Materials • Summary eoul National University 2/23 CHANGHEE LEE | Organic S CHANGHEE LEE | Organic S emiconductor Lab. | S emiconductor Lab. | S eoul National University
Korea-US NanoForum 2010 Nanoparticle applications ECC, Ewha Univ., Korea 2010. 4. 5-6 • Quantum dots Q – QDLEDs – Solar cells – Biomedicine • Magnetic nanoparticles – Biomedicine: MRI. Hyperthemia, Drug delivery • Metal nanoparticles – Biodetection (Au. Ag) QLED & Display – Electromagnetic shell (Fe, Ni, Co) – Nanofluid • Metal oxide nanoparticles – Dielectrics - + – Nanocomposite Al Active Layer – Nanocoating PEDOT:PSS PEDOT PSS ITO Biomarkers SAIT W. U. Huynh, J. J. Dittmer, A. P. Alivisatos, Science, 295, 2425 (2002) A. P. Alivisatos, Science (1998) NANOCO eoul National University 3/23 CHANGHEE LEE | Organic S CHANGHEE LEE | Organic S emiconductor Lab. | S emiconductor Lab. | S eoul National University
Korea-US NanoForum 2010 Comparison of QD-LED and OLED ECC, Ewha Univ., Korea 2010. 4. 5-6 F Feature t QD LED QD-LED OLED OLED Efficiency Low High Emission bandwidth Narrow Broad (color saturation) FWHM<30nm FWHM<50-100 nm Excellent: Low: Color Tunability Change QD size Different emitter Low: Cost of Emitter One procedure for all p High g RGB emitters Vacuum deposition Manufacturing process Solution-based Solution-based J. H. Kwak, Ph.D. Thesis (SNU, 2010) Large display area Yes Yes Flexibility Yes Yes J. H. Kwak et al., SID 2010 J. H. Kwak, Ph.D. Thesis (SNU, 2010) eoul National University 4/23 CHANGHEE LEE | Organic S CHANGHEE LEE | Organic S emiconductor Lab. | S emiconductor Lab. | S eoul National University
Korea-US NanoForum 2010 LEDs based on colloidal quantum dots ECC, Ewha Univ., Korea 2010. 4. 5-6 QD-LEDs e injection QDs HTL HTL ETL p cathode cathode • Size-tunable band-gaps (Color tunability) Light • High PL quantum efficiency • Good photostability anode • Narrow emission line widths (FWHM N i i li idth (FWHM <30 nm) • Compatibility with solution processing h injection methods methods e-h Recombination eoul National University 5/23 CHANGHEE LEE | Organic S CHANGHEE LEE | Organic S emiconductor Lab. | S emiconductor Lab. | S eoul National University
Korea-US NanoForum 2010 QD LEDs Tunable over the Entire Visible Spectrum ECC, Ewha Univ., Korea 2010. 4. 5-6 Polina O. Anikeeva, Jonathan E. Halpert, Moungi G. Bawendi and Vladimir Bulovic ( MIT ), Nano Lett., 2009, 9 (7), pp 2532–2536 eoul National University 6/23 CHANGHEE LEE | Organic S CHANGHEE LEE | Organic S emiconductor Lab. | S emiconductor Lab. | S eoul National University
Korea-US NanoForum 2010 Problems for low efficiency of colloidal QD-LEDs ECC, Ewha Univ., Korea 2010. 4. 5-6 Poor charge carrier injection because Poor charge carrier injection because • Wide energy band gap shell Wid b d h ll • Organic ligands 1) QDs generally have an inorganic shell of a wide • Surface traps bandgap material (e.g., CdS or ZnS) to increase photostability and improve emission quantum yields by passivating surface defects. HIL/ HTL 2) QDs are covered by a layer of organic ligands , 2) QDs are covered by a layer of organic ligands , organic organic QD which is needed during their growth and provides solubility in organic solvents to allow processing. 5~5.5 eV However, these organic and inorganic layers form H h i d i i l f 6.5~7.3 eV a tunneling barrier for charge injection. 1~2 eV gap 3) The valence bands of the QDs are generally shifted ) g y Top view T i X X-section view ti i to lower energy compared to the highest occupied molecular orbital (HOMO) levels of commonly used organic hole injection layers This introduces used organic hole-injection layers. This introduces significant energy barriers to hole injection . 4) Massive QD aggregation occurs in blend film of QDs and polymers � Poor morphology eoul National University 7/23 CHANGHEE LEE | Organic S CHANGHEE LEE | Organic S emiconductor Lab. | S emiconductor Lab. | S eoul National University
Korea-US NanoForum 2010 Conducting Polymer - Nanoparticle Hybrid System ECC, Ewha Univ., Korea 2010. 4. 5-6 Nanoparticle op c e Conducting Polymer/NP Hybrid C d i l / b id • High extinction coefficient • High electron mobility • Band gap & position tunability • Solution process capability Polymer SH SH S SH SH SH • High extinction coefficient • High extinction coefficient • Efficient charge separation • High hole mobility • Improved colloidal stability • Solution process capability • Solution process capability • Patterning capability • Patterning capability • Patterning capability i bili • Synthesis thru RAFT, ATRP, NMP eoul National University 8/23 CHANGHEE LEE | Organic S CHANGHEE LEE | Organic S emiconductor Lab. | S emiconductor Lab. | S eoul National University
Korea-US NanoForum 2010 Quantum Dot / Conducting Polymer Hybrid ECC, Ewha Univ., Korea 2010. 4. 5-6 SH m n O NH SH N poly(TPA)-b-cysteaminacrylate Evidence of hybridization * UV illumination (365 nm, 2 mW/cm 2 ) hexane dimetyhlformamide Matthias Zorn, Wan Ki Bae, Jeonghun Kwak, Hyemin Lee, Changhee Lee, Rudolf Zentel, Kookheon Char, ACS Nano 3 (5), 1063 (2009) eoul National University 9/23 CHANGHEE LEE | Organic S CHANGHEE LEE | Organic S emiconductor Lab. | S emiconductor Lab. | S eoul National University
Korea-US NanoForum 2010 Comparison of QD/Polymer Hybrid and Blend ECC, Ewha Univ., Korea 2010. 4. 5-6 • Quantum Dot / Conducting Polymer Hybrids Q t D t / C d ti P l H b id The thiol anchor groups in the CAA block replace the surface ligands (oleic acid) of QDs, leading to QD/conducting polymer hybrid films. * poly( para methyl triphenylamine- b -cysteamine acrylamide) • Quantum Dot / Conducting Polymer Blends The fluorinated block (PFP) with low surface (PFP) ith l f energy does not have specific interactions with QDs, resulting in QD/ QD/conducting polymer d ti l blend films. * poly( para methyl triphenylamine- b -pentafluorophenole) Jeonghun Kwak, Wan Ki Bae, Matthias Zorn, Heeje Woo, Hyunsik Yoon, Jaehoon Lim, Sang Wook Kang, Stefan Weber, Hans-Jürgen Butt, Rudolf Zentel, Seonghoon Lee, Kookheon Char, Changhee Lee, Adv. Mater. 21 (48), 5022 (2009) eoul National University 10/23 CHANGHEE LEE | Organic S CHANGHEE LEE | Organic S emiconductor Lab. | S emiconductor Lab. | S eoul National University
Korea-US NanoForum 2010 Comparison of QD/Polymer Hybrid and Blend ECC, Ewha Univ., Korea 2010. 4. 5-6 QD+polymer Pristine QDs (OA) blends blends QD/Polymer Hybrids a. u.) ntensity (a PL In PTPA- b - CAA 400 450 500 550 600 Wavelength (nm) About 80 % of the PL intensity remains after grafting the QD surfaces with block copolymer copolymer. eoul National University 11/23 CHANGHEE LEE | Organic S CHANGHEE LEE | Organic S emiconductor Lab. | S emiconductor Lab. | S eoul National University
Korea-US NanoForum 2010 Comparison of QD/Polymer Hybrid and Blend ECC, Ewha Univ., Korea 2010. 4. 5-6 Hybrid Film Fluorescent Optical Microscopy Optical Microscopy Blend Film * All films were fabricated by spin- coating coating. eoul National University 12/23 CHANGHEE LEE | Organic S CHANGHEE LEE | Organic S emiconductor Lab. | S emiconductor Lab. | S eoul National University
Korea-US NanoForum 2010 Comparison of QD/Polymer Hybrid and Blend ECC, Ewha Univ., Korea 2010. 4. 5-6 Hybrid Films TEM top view * All films were fabricated by spin-coating. QD 0.5 wt% QD 1.0 wt% QD 1.5 wt% * Scale bars in the figure are 200 nm. Blend Films QD 0.5 wt% QD 1.0 wt% QD 1.5 wt% Hybrid and Blend films show drastic differences. H b id d Bl d fil h d i diff eoul National University 13/23 CHANGHEE LEE | Organic S CHANGHEE LEE | Organic S emiconductor Lab. | S emiconductor Lab. | S eoul National University
Korea-US NanoForum 2010 Comparison of QD/Polymer Hybrid and Blend ECC, Ewha Univ., Korea 2010. 4. 5-6 Hybrid Films TEM top view TEM cross-section view QD 0.5 wt% QD 1.0 wt% QD 1.5 wt% * Scale bars in the figure are 200 nm. Blend Films QD 0.5 wt% QD 1.0 wt% QD 1.5 wt% A Aggregation & phase separation within blend films. i & h i i hi bl d fil eoul National University 14/23 CHANGHEE LEE | Organic S CHANGHEE LEE | Organic S emiconductor Lab. | S emiconductor Lab. | S eoul National University
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